Sensory inspection of food is a method to record various quality characteristics of food by language, characters, symbols or data according to the "feelings" of human sensory organs such as taste, smell, vision and hearing, and then make statistical analysis by using the principle of probability statistics, so as to draw a conclusion and evaluate the color, aroma, taste, shape, quality and taste of food.
(1) The significance of food sensory inspection ① Judging the acceptability of food; ② Identify the quality of food. Sensory inspection can not only directly judge the sensory characteristics of food, but also detect whether there are abnormal phenomena, and accordingly put forward necessary physical and chemical inspection and microbial inspection items to facilitate the detection and control of food quality.
(2) The quality characteristics of food are inherent in the product, and are not influenced by human feelings, but only differentiated according to the physical and chemical state of the product, such as the size, weight and color of the product. People's faculties are used for inspection, such as knocking on cans and judging the maturity of watermelons. Characteristics influenced by people's feelings and hobbies, such as the taste, packaging and decoration of food.
1. 1 sensory test type
According to different functions, it can be divided into two types.
1. 1. 1 analytical sensory test
Analytical sensory inspection is to use human sensory organs as a tool for inspection and measurement, to evaluate the quality characteristics of samples or to identify the differences between multiple samples.
Analytical sensory testing is based on the sense of sensory organs. Therefore, in order to reduce the influence of individual senses, improve the reproducibility of the test and obtain high-precision results, we must attach importance to the standardization of evaluation standards, the standardization of test conditions and the selection of evaluator's quality.
(1) standardization of evaluation criteria In the sensory inspection of food quality characteristics, there must be clear and specific evaluation criteria and evaluation criteria, that is, the evaluation criteria should be unified and standardized, so as to avoid evaluators using their own evaluation criteria and criteria, making it difficult to unify and compare the results. When sensory testing is carried out on the same food, the standards and evaluation standards must be consistent and stable. Therefore, it is standardized to make standard samples.
(2) Standardized sensory test of experimental conditions, the analysis results are easily influenced by environment and experimental conditions, so the experimental conditions should be standardized, such as having a suitable sensory laboratory and proper lighting to prevent the experimental results from fluctuating greatly due to the influence of environment and conditions.
(3) the quality of the evaluator An evaluator engaged in sensory testing must have good physical and psychological conditions, be properly trained and have keen senses.
To sum up, analytical sensory test is an objective evaluation of the object by the evaluator, and its analysis results are not interfered by people's subjective will.
1. 1.2 preferred sensory test
Preference-oriented sensory testing takes samples as tools to understand people's sensory reactions and tendencies. This test must be carried out by human senses, and the procedure of the influence of quality characteristics on people's feelings and hobbies is completely investigated and studied by human instruments. The main problem of this test is how to objectively evaluate the distribution tendency of different testers' feelings and hobbies.
1.2 development process of sensory testing
1935, the famous British statistician R.A.Fisher applied statistical methods to sensory testing for the first time in his works. In 1936, S.Keber really applied statistical methods to sensory inspection, and used two-point test method to test meat tenderness for the first time. At 194 1, Whi, the owner of an American factory,
Statistics, physiology and psychology are the three scientific pillars of sensory testing.
Applications in food industry: identification of wine taste and food freshness, inspection of canned containers and contents, visual inspection of frozen meat deterioration, aroma inspection of spices, bubble inspection of beer, aroma inspection of soy sauce, food packaging inspection, etc.
1.3 the concept of feeling
1.3. 1 the definition of feeling
Feeling is the various characteristics and attributes of objective things, which cause exciting reactions by stimulating different sensory organs of people and reflect them to the nerve center of cerebral cortex through nerve conduction. A feature or attribute produces a feeling, and the synthesis of feelings forms people's understanding and evaluation of this thing.
1.3.2 classification and sensitivity of sensation
Human senses are divided into five basic senses, namely, sight, hearing, touch, smell and taste. In addition to the above five basic senses, human recognizable senses include temperature, pain, fatigue and taste.
Sensory sensitivity refers to the ability of human sensory organs to feel, identify and distinguish stimuli. Sensory sensitivity varies from person to person, and some senses can be specially developed through training or strengthening, that is, sensitivity enhancement.
1.3.3 sensory threshold
Inducing sensation requires appropriate stimulus intensity, which is called sensory threshold. It refers to the range of stimulus intensity from only causing sensation to only not causing sensation. The concept of dose expresses their stimulation intensity, time and relationship. For food, in order to make people feel the existence of a certain taste, the dosage of the substance must exceed its taste threshold.
Sensory threshold: refers to the upper and lower limits of the acceptable stimulus range and the sensitivity to the smallest change within this range.
According to the different measurement techniques and purposes, the concept of sensory threshold can be divided into the following categories.
(1) Absolute sensory threshold refers to the range of stimulus intensity, with the lowest stimulus amount that makes human senses feel as the lower limit and the highest stimulus amount that leads to sensory disappearance as the upper limit.
1 (2) Perception threshold We call it the perception threshold or the lower limit of the perception threshold that can just cause the smallest stimulus of sensation.
(3) Recognition threshold refers to the minimum stimulus that can cause definite sensation.
(4) Limit Threshold For the maximum stimulus that just caused the sensation to disappear, we call it the upper limit of the sensation threshold, also known as the limit threshold.
(5) Difference threshold refers to the minimum change of stimulus that can be felt by the senses. For example, the wavelength difference of light wave change that people feel is l0nm. The difference threshold is not a constant value, but changes with some factors such as environmental, physiological or psychological changes.
1.4 basic law of sensation
1.4. 1 adaptation (except pain)
It refers to the phenomenon that the sensitivity of receptors changes under the continuous action of the same stimulus.
1.4.2 Contrast phenomenon (quantitative influence)
When two different stimuli act on the same receptor successively, the phenomenon that one stimulus is stronger than the other is generally called contrast phenomenon, and the resulting reaction is called contrast effect.
Because of the phenomenon of taste contrast, the threshold of the second flavor substance has also changed. In the development of food formula, we can use the phenomenon of taste contrast to add some flavor-presenting substances purposefully to make the expected taste stand out or cover up the bad taste.
1.4.3 Synergy and antagonism
When two or more stimuli act on the same sensation at the same time, the phenomenon that the sensory level exceeds the superposition of individual effects of each stimulus is called synergistic effect or multiplier effect.
For example, the combination of flavor substances A and B has greater flavor intensity than single A or B (salt+glutamic acid, sodium inosinate).
In food processing, using the multiplication effect of flavor can improve the flavor intensity of flavor-presenting substances, reduce costs and get twice the result with half the effort.
Contrary to synergistic effect, antagonistic effect is a phenomenon that the intensity of one stimulus is weakened by the existence of another stimulus. For example, the killing effect of essence: 15%NaCl salt water is unbearable; Soy sauce containing 15%NaCl, because it contains amino acids, sugars and organic acids, weakens the salty taste of NaCl.
1.4.4 masking phenomenon
When two stimuli with different intensities act on the same feeling at the same time, only one of them can be felt, which is called masking phenomenon.
2. Sensory evaluation of food
2. 1 vision and visual evaluation
2. 1. 1 Generation and characteristics of vision
(1) Generation of visual illumination → Waves from objects → Formation of retinal images → Stimulation of sensory cells → Optic nerve → Visual center → Vision.
(2) The intensity of characteristic vision depends on the wavelength and intensity of light.
2. 1.2 Visual inspection
Appearance, luster, color
2.2 Auditory and auditory evaluation
2.2. 1 hearing production and characteristics
(1) Sound waves generated by hearing → tympanic membrane → stimulation of cochlear receptors → auditory nerve → auditory pathway.
(2) The pitch of the frequency. The absolute sensory threshold of frequency is 65438 06 ~ 20000 Hz.
Evaluation of the hearing
The human ear is very sensitive to small changes in sound intensity or frequency, and the application of auditory sensory testing is very extensive.
2.3 evaluation of sense of smell and sense of smell
2.3. 1 sense of smell and its characteristics
Olfactory area: the olfactory mucosa in the olfactory area is the olfactory receptor, and olfactory cells are the most important components in the olfactory receptor.
The production of sense of smell; Smell → olfactory cells → brain → olfactory nerve
Stimulants must be volatile and soluble.
Due to the adaptability of the senses, the evaluation is to smell lightly and smell again.
Olfactory evaluation
Smell plays a very important role in food production, inspection and identification. There are many aspects that cannot be replaced by instruments and physical and chemical tests.
2.4 Taste and taste evaluation
2.4. 1 The Generation and Characteristics of Taste
(1) produces soluble flavor substances → taste buds (taste cells) → brain → taste.
(2) Different parts of the feature are sensitive to different tastes, and the sensitivity to different tastes is also different.
(3) The influencing factors are water solubility, temperature, sex, age, physical condition, hunger, chemical structure and optical properties of odorous substances.
2.4.2 Taste evaluation
Generation of stimulus: weak → strong
Flavoring phenomenon and effect: contrast, tone sandhi, multiplication and killing each other.
2.5 Tactile and Tactile Assessment
2.5. 1 Touch and its characteristics
Touch: The feeling of skin is called touch.
Hot and cold spots on the skin → thermal stimulation 10 ~ 600℃.
Tactile sensitivity
Tactile receptors are unevenly distributed in the skin, and fingertips are the most sensitive. There are more cold spots on the skin than warm spots, so people are highly sensitive to cold.
2.5.3 tactile sensory evaluation
Tactile sensory evaluation is a kind of sensory evaluation to distinguish and judge the quality characteristics of products through the feeling produced when people's hands and skin surfaces contact objects.
2.6 Evaluation of taste
Physical feelings: hardness, viscosity, elasticity, brittleness, chewiness, etc.
2.7 Basic requirements of sensory evaluation
Evaluator: the type of evaluator.
Number of evaluators
Basic conditions and threshold test of appraisers
Selection of evaluators and sensitivity test of training
Dilution test
Environment (laboratory requirements)
Physical conditions of inspection
Electrical appliances and water
sample
Preparation of the sample to be tested
sample distribution